Our genomes are mostly made up of repetitive 'junk DNA' derived from insertions of sequences through RNA intermediates. Our group has developed methods to identify polymorphic insertions of these understudied sequences, demonstrated they are major sources of structural variation our genome, and found they occur frequently in LD with trait associated SNPs identified by cancer genome wide association study (GWAS). Experiments by others and characterizations of the non-random distribution of mobile DNAs in our genome indicate they have significant potential to effect gene function. The overarching hypothesis of this proposal is that a subset of common mobile DNA insertions predispose to common cancer development. Our three part approach to test this hypothesis will include: (i.) identification of RIPs with potential roles in neoplasia by locating those in the vicnity of regions implicated in disease risk by GWAS; (ii.) determining which of these RIPs may reasonably account for cancer risk by analyses of area linkage and RIP genotype imputing in clinical samples; and (iii.) investigating effects of transposon polymorphisms on transcript expression levels and structure. Hematopoietic malignancies will receive special priority in these studies, and clinical samples from patients with leukemias, lymphomas, and related disordered will be used for a directed RIP discovery effort and for evaluating mechanisms of gene expression effects.